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题解 | 问GPT之前先动手画个表格把关系梳理清楚

select name u_n,lo.date date,sum(number)over(partition by lo.user_id order by lo.date) ps_num from login lo right join passing_number pn on lo.user_id...

SQL错题

2023-12-05

1 247

题解 | #牛客每个人最近的登录日期(四)#

# 每个日期新登录个数 /*SELECT dates.date, IFNULL(new_users.new, 0) AS new FROM ( SELECT DISTINCT date FROM login ) AS dates LEFT JOIN ( SELECT f...

SQL错题

2023-12-03

0 229

题解 | where exists

SELECT ROUND( (SELECT COUNT(DISTINCT user_id) FROM login a WHERE EXISTS ( SELECT 1 FROM login AS b WHERE a...

SQL错题

2023-12-03

0 314

题解 | case的用法

SELECT e.emp_no, e.first_name, e.last_name, eb.btype, s.salary, CASE WHEN eb.btype = 1 THEN ROUND(s.salary * 0.1, 1) WHEN eb.btype = 2 THEN ...

SQL错题

2023-11-25

0 260

题解 | sum()over()累计求和

select emp_no,salary,sum(salary)over(order by emp_no) running_total from salaries where to_date='9999-01-01'

SQL错题

2023-11-25

1 235

题解 | %是一个运算符，用于返回除法的余数。

/*SELECT first_name FROM ( SELECT first_name, ROW_NUMBER() OVER (ORDER BY first_name) as row_num, ROW_NUMBER() OVER (ORDER BY emp_no) as original_...

SQL错题

2023-11-25

0 438

题解 | not exists

/*select em.emp_no emp_no,birth_date,first_name,last_name,gender,hire_date from employees em left join dept_emp de on em.emp_no=de.emp_no where dept_n...

SQL错题

2023-11-23

0 268

题解 | limit+查询行数 offset+跳过前几行

select * from employees limit 5 offset 5

SQL错题

2023-11-23

0 228

题解 | 聚合函数不能直接在where字句中使用

select avg(salary) avg_salary from salaries where to_date='9999-01-01' and salary>(select min(salary) from salaries where to_date='9999-01-01') and...

SQL错题

2023-11-23

0 273

题解 | SEPARATOR关键字用于指定连接时使用的分隔符

SELECT dept_no, GROUP_CONCAT(emp_no SEPARATOR ',') AS employees FROM dept_emp GROUP BY dept_no;

SQL错题

2023-11-22

0 213